The main purpose of our investigation is to evaluate the diagnostic validity of DSM-III anxiety disorders of childhood and adolescence. This will be accomplished by examining familial aggregation and longitudinal outcome of separation anxiety disorder and overanxious disorder, with children and adolescents who meet DSM-III criteria for these disorders. The family study will allow us to determine whether separation anxiety and overanxious disorders aggregate in families of child probands with these diagnoses. The follow-up study will enable us to evaluate the clinical course and outcome (prognosis) of the two anxiety disorders. Sixty children and adolescents with separation anxiety disorder, 60 children and adolescents with overanxious disorder, 60 children and adolescents with attention deficit disorder, and 60 children and adolescents who have never been psychiatrically ill will participate in the project. During the family study, the first- and second-degree relatives of probands in each of these groups will be evaluated for current and past psychiatric illness. The follow-up study will include re-evaluations of probands at 12 and 24 months following their initial (intake) diagnostic assessments. Comparison of the separation anxiety disorder and overanxious disorder groups with nonanxious psychopathological and never psychiatrically ill controls will enable us to determine: 1) the diagnostic specificity of findings for the two anxiety disorder groups, and 2) the statistical and clinical significance of results for the anxiety groups, for both the family and follow-up studies.